1. Field of the Invention
The present invention relates to a navigation device for performing a route guidance and a method of navigating a vehicle.
2. Description of Related Art
A navigation device for a vehicle performs route guidance. First, the navigation device searches a suitable route from a departure place, e.g., present position, to a destination place for the vehicle. Then, the navigation device displays the suitable route in a road map on a display screen, and a driver drives the vehicle along the suitable route. Before the vehicle passes through a guidance point (e.g., intersection) of the suitable route, a direction (e.g., left or right) to which the vehicle turns is displayed in the road map. At the same time, voice guidance indicates the direction.
However, in this case, the driver of the vehicle has to recognize a relationship between the present position of the vehicle and the guidance point. When the guidance point has no sign, the driver may not be able to recognize the present position as the guidance point.
JP-A-2001-324348 discloses a navigation device for a vehicle. This navigation device helps the driver to recognize the present position as the guidance point, because the voice guidance makes the driver to find a landmark for the guidance point. The landmark is a convenience store or a public building such as a post office, for example.
JP-A-2001-74477 discloses another navigation device. This navigation device displays a three-dimension real image of the guidance point seen from the vehicle, before the vehicle passes through the guidance point. The real image is made of a picture really taken, or a computer graphic (CG) image. The real image is usually displayed on the display screen together with the road map, in order to help the driver to recognize the guidance point.
However, the landmark may disappear, because the convenience store may be closed. Further, a name of the public building may be changed. In these cases, the voice guidance may be incorrect, because the landmark no longer exists. Thereby, the driver may be confused, or drive along a wrong route. Therefore, a map data of the navigation device has to be updated. However, the update of the map data is practically difficult.
Further, the driver needs a certain time for comparing the three-dimension real image with a true view (scenery), because the three-dimension real image has a large amount of information. Thus, a task for the driver may be unnecessarily increased.